Breather structure for internal combustion engine

Abstract

A breather structure for internal combustion engine, the structure making a breather chamber smaller and thus making an internal combustion engine as a whole smaller. A breather chamber and a small chamber are formed. The breather chamber includes a first side face cover. The first side face cover is joined to a case to cover a first one of the right and left side faces of the case. Inside the first side face cover, an auxiliary apparatus chamber is formed. The auxiliary apparatus chamber houses a clutch mechanism connecting or disconnecting the power transmission route. Additionally, formed inside a housing are an external communication port communicating to the outside of the housing, and the small chamber communicating to a crank chamber and to the auxiliary apparatus chamber. Moreover, the auxiliary apparatus chamber communicates to the breather chamber.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2006-094412, filed Mar. 30, 2006, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a breather structure for an internal combustion engine with a cylinder block and a case joined to the cylinder block. The cylinder block has a cylinder bore formed therein, and a piston, which is disposed in the cylinder bore by being inserted thereinto, and which can reciprocally travel freely in the cylinder bore. Meanwhile, the case has a crank chamber communicating to the cylinder bore. A crankshaft is housed in the crank chamber, while the crankshaft rotates in conjunction with the piston. [0004] 2. Description of Background Art [0005] In such an internal combustion engine, the internal pressure of the crank chamber, which communicates to t...

AI Technical Summary

Benefits of technology

[0011] In the breather structure for internal combustion engine, configured as described above, an increased internal pressure in the crank chamber is lowered once in the small chamber, and then is lowered further in the auxiliary apparatus chamber which has a large capacity, and in which the clutch mechanism is housed. As has just been described, the crank chamber does not directly communicate to the auxiliary apparatus chamber, so that the fluctuation in pressure inside the auxiliary apparatus chamber can be made smaller. Additionally, this auxiliary apparatus chamber communicates to the breather chamber, while the breather chamber communicates to the outside of the housing through the external communication port. The small chamber provided as has just been described makes the mitigation of the pressure fluctuation in the auxiliary apparatus chamber so effective that a smaller breather chamber than that of the conventional breather structure can have a sufficient breathing effect. As a result, the internal combustion engine as a whole can be made smaller in size.

[0012] Additionally, in a configuration with shaft members of the power transmission system being housed in the crank chamber, a transmission mechanism, such as gears, is provided around the shaft members. Such a configuration tends to produce a dead space in an outer peripheral portion of the transmission mechanism. The breather chamber with a smaller capacity and the smaller chamber can be provided inside the case by making use of this dead space. Such effective use of a space makes it unnecessary to provide special members dedicated to form the small chamber and the breather chamber. This simplifies the housing structure of the power transmission system and of the internal combustion engine. As a result, an internal combustion engine produced at a lower cost can be provided.

[0013] At this time, when the gears constituting the transmission mechanism of the power transmission system are housed in the crank chamber, an area, overlapping the gears when viewed from a side, is formed in the auxiliary apparatus chamber, which is formed inside the first side face cover that covers one of the right and left side faces of the case. Here, the breather entrance port that allows the auxiliary apparatus chamber to communicate to the breather chamber is formed on a first side of the gears while a communication port that allows the auxiliary apparatus chamber to communicate to the small chamber is formed on the second side of the gears. With this configuration, the distance between the breather entrance port and the communication port can be made longer than otherwise. Accordingly, making use of the space overlapping the gears when viewed from a side, mitigation of the fluctuation in the internal pressure can be carried out effectively with the auxiliary apparatus chamber. In addition, by delimiting the inside of the auxiliary apparatus chamber, the auxiliary chamber is formed in the area overlapping the gears when viewed from a side, while the auxiliary chamber is allowed to communicate to the breather chamber. Accordingly, by making use of this auxiliary chamber, further mitigation of the fluctuation in pressure is pursued, and the capacity of the breather chamber can be made even smaller.

[0014] Moreover, the small chamber communicates to the second auxiliary apparatus chamber formed inside the second side face cover, which covers the second side face of the right and the left side faces of the case. Accordingly, the second auxiliary apparatus chamber can be made use of for the purpose of mitigating the pressure. As a result, the fluctuation in the pressure inside the clutch chamber can further be mitigated, and the capacity of the breather chamber can be made still even smaller.

Problems solved by technology

Such a breather structure, however, makes the impact of the fluctuation in the pressure in the crank chamber great because the clutch chamber directly communicates to the crank chamber.

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